The present invention is directed to flame retardant carbonate polymer compositions and articles prepared therefrom. The carbonate polymer contains a flame retardant additive comprising metal salts of highly fluorinated methides, imides or amides. The composition provides flame retardancy at relatively low levels of additive, may allow a broader processing window of additive compositions and can have high transparency.
Carbonate polymers, derived from the reaction of bis-hydroxy or dihydroxy compounds with carbonic acid derivatives are widely used because of their desirable physical and chemical properties. In particular, carbonate polymers are used in the manufacture of molded parts wherein rigidity, impact strength, toughness, ductility, heat stability, clarity and high dielectric properties are desired. Unfortunately, the carbonate polymers may exhibit a burning time when contacted with an open flame, and so are precluded from many applications for safety reasons. Many carbonate polymers, particular those derived from bisphenol-A, are classified as V-2 in the burning test defined in Underwriter""s Laboratories Tests for Flammability of Plastic Materials test UL 94, of May 14, 1993.
Polycarbonates have been modified with various additives in attempts to reduce the flammability (or increase the combustion resistance). Such additives have included phosphites, phosphates, thiophosphoric acid esters containing halogenated alkyl radicals and other halogenated organic compounds. With many such additives, they must be added at relatively high weight percentages that may adversely affect the physical and/or optical properties of the resulting articles. Polytetrafluoroethylene has been added, as an anti-drip and flame retardant agent, to polycarbonate resins, but adversely affects the clarity and transparency of molded articles made therefrom. Glass fibers may be added, but the addition adversely affects the polymer matrix and optical properties. In many applications, the polycarbonate molding composition is rendered opaque by the addition of pigments to mask the reduced optical properties.
Perfluoroalkyl sulfonate salts have been added to polycarbonates. While they reduce the flammability of the resulting articles, they have a very narrow window of processibility. Too low a concentration and the flammability is not sufficiently reduced. Too high a concentration and the optical properties, such as transparency and clarity, suffer.